Semiconductor manufacturing includes the process of moving semiconductor substrate dies from a wafer table to a lead frame after they have been cut from a silicon wafer of substrate material. A silicon wafer first is placed on an adhesive surface and is cut into rectangular dies. After cutting, the adhesive surface is placed on a wafer table of a die bonder apparatus. The die bonder deposits an adhesive on the lead frame, removes a cut die from the adhesive surface, and places it on the lead frame on the deposited adhesive. The silicon wafer from which the dies are cut is round, such that some dies are not fully rectangular. These nonrectangular dies will be left on the adhesive surface and discarded.
If the process of removing dies from a silicon wafer is automated, the position of the silicon wafer and dies must be known or estimated, to allow a robot arm to manipulate the wafer and dies. Nevertheless, the position of the silicon wafer with respect to the known coordinates of the adhesive surface may randomly change during the die cutting operation. When such random changes occur, no die may be present at some locations in which a die is expected. This condition may result in unnecessary wafer table movements to locate the cut dies.
To prevent this condition from occurring, known methods of automating the removal of cut dies from a silicon wafer typically include conservative assumptions about the location of the wafer on the wafer table. These assumptions may result in a loss of usable cut dies, or the performance of additional robot arm movements that increase the time needed to remove the cut dies.